A study on tidal force/stress triggering of strong earthquakes
一种新型随钻电阻率测井仪器的响应和刻度

The distribution of electromagnetic fields and the feature of receiver coil's response for a new logging-while-drilling resistivity tool in homogeneous earth are analyzed, and the calibration method of the tool in vacuum is studied. The vector eigen function expansion formulae of the dyadic Green's functions with magnetic current source in radial layered medium are derived in cylindrical coordinate system, and hence the needed analytical formulae are obtained to study the distribution of electromagnetic fields, the receiver coil's response and the calibration method of the tool. It is shown through computation that the orientative exploring capacity of the tool is greatly enhanced because of the existence of the drill collar. It is also shown that different size of the drill collar and different distance between the coils and the drill collar have obviously different influence on the response of the coils in vacuum. The real-part signal produced by the drill collar in the earth can be approximately regarded as constant, and the imaginary part can also be approximately regarded as constant when the conductivity of the earth is greater than 0.01S/m. Numerical computation has shown that the bigger the tool's eccentricity level and the drill collar's radius, the smaller the apparent conductivity of the calibration ring's resistance.